An intake pipe is provided internally with a throttle valve for controlling an intake amount. A problem arises in that an unusual noise occurs when the throttle valve is opened abruptly. In order to suppress the occurrence of such an unusual noise, there is a know technique for regulating the airflow by providing a flow-regulating net portion constituted by a linear portion having a mesh shape on the downstream side of the throttle valve. There is also a known technique for providing this flow-regulating net portion in an annular gasket that seals a gap between an end surface of one of two pipes constituting the intake pipe and an end surface of the other pipe thereof. In these techniques, the flow-regulating net portion is generally constituted by a material having high rigidity such as metal, and the gasket is constituted by an elastic body such as rubber. However, such a constitution involves significant costs, and in this respect, there is also a known intake noise reduction device in which the flow-regulating net portion is also constituted by an elastic body, and a gasket portion are provided in integrated fashion (see PTL 1).
When the flow-regulating net portion is made of an elastic material, it is prone to deform, unlike the design wherein it is made of high-rigidity material such as metal. Therefore, a flow-regulating net portion made of an elastic material should desirably be designed to hardly deform, in order to enhance the durability. One possibility is to make the linear parts that form the flow-regulating net portion thicker. With merely thicker linear parts, however, the mesh interstices will be smaller and the airflow will be hindered. With the airflow impeded, the flow amount is reduced, which may deteriorate the combustion efficiency, since a necessary amount of air may not be supplied to the engine. Therefore, simply making the linear parts thicker is not sufficient as a measure to suppress deformation of the flow-regulating net portion.